/// <summary>
/// Called to return a block to the pool. Once Return has been called the memory no longer belongs to the caller, and
/// Very Bad Things will happen if the memory is read of modified subsequently. If a caller fails to call Return and the
/// block tracking object is garbage collected, the block tracking object's finalizer will automatically re-create and return
/// a new tracking object into the pool. This will only happen if there is a bug in the server, however it is necessary to avoid
/// leaving "dead zones" in the slab due to lost block tracking objects.
/// </summary>
/// <param name="block">The block to return. It must have been acquired by calling Lease on the same memory pool instance.</param>
internal void Return(MemoryPoolBlock block)
{
#if BLOCK_LEASE_TRACKING
Debug.Assert(block.Pool == this, "Returned block was not leased from this pool");
Debug.Assert(block.IsLeased, $"Block being returned to pool twice: {block.Leaser}{Environment.NewLine}");
block.IsLeased = false;
#endif
if (!_isDisposed)
{
_blocks.Enqueue(block);
}
else
{
GC.SuppressFinalize(block);
}
}
/// <summary>
/// Internal method called when a block is requested and the pool is empty. It allocates one additional slab, creates all of the
/// block tracking objects, and adds them all to the pool.
/// </summary>
private MemoryPoolBlock AllocateSlab()
{
var slab = MemoryPoolSlab.Create(_slabLength);
_slabs.Push(slab);
var basePtr = slab.NativePointer;
// Page align the blocks
var offset = (int)((((ulong)basePtr + (uint)_blockSize - 1) & ~((uint)_blockSize - 1)) - (ulong)basePtr);
// Ensure page aligned
Debug.Assert(((ulong)basePtr + (uint)offset) % _blockSize == 0);
var blockCount = (_slabLength - offset) / _blockSize;
Interlocked.Add(ref _totalAllocatedBlocks, blockCount);
MemoryPoolBlock block = null;
for (int i = 0; i < blockCount; i++)
{
block = new MemoryPoolBlock(this, slab, offset, _blockSize);
if (i != blockCount - 1) // last block
{
#if BLOCK_LEASE_TRACKING
block.IsLeased = true;
#endif
Return(block);
}
offset += _blockSize;
}
return(block);
}
